Self-contained hydraulic tappet



' Aug. 27, 1957 P. F. BERGMANN y SELFQCONTAINED HYDRAULIC TAFPET FiledNov. 22, 1954 .fi-E

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ffm E ,emma/mf W EX l I ATTORNIEf/xu snLF-coNrArNnD HYDRAULIC TAPPETPaul F. Bergmann, Muskegon, Mich., assignor to Johnson Products, Inc.,Muskegon, Mich., a corporation of Michigan Application November 22.,1954, Serial No. 470,210 7 Claims. (Cl. 12S-90) The present inventionrelates to hydraulic tappets for internal combustion engines, whichtappets are self-adjusting and carry within the body of the tappet alixed quantity of hydraulic liquid. It is a primary object and purposeof the present invention to provide a practical, economical and simplehydraulic tappet, the liquid which is used being placed within thetappet when it is assembled, and which does not need to be replenishedor replaced during the life of the engine.

The present tappet of my invention, diiering from hydraulic tappetswherein the oil is continuously supplied from the lubricating system ofthe engine, does not require that the guides for the moving tappets haveoil conducting passages leading thereto to supply them with oil from theengine lubricating system under pressure.

With the hydraulic tappets in general use today, it is necessary to usewhatever oil may be in the engine at whatever condition the oil may be,and dirty or deteriorated oil frequently causes hydraulic tappetfailures. In the present invention the lubricating oil of the engine isof no importance with relation to the tappets, their operation andfunctioning.

One feature of the present invention is that the hydraulic liquid whichis used is a silicone oil, or silicone uid. This is a synthetic oilwhich has certan propertes partcularly suitable for use in a hydraulictappet. For one thing, the viscosity is almost uniform from the lowtemperatures encountered in our northern climate to the hightemperatures to which oil is subjected in an internal combustion engine.While there is some change in viscosity over this range of temperature,it is so much less than the variation in viscosity of petroleum oil overthe same temperature range, that the problem of metering the leak-by ofoil from the pressure chamber to the reservoir chamber of a hydraulictappet is much simplified. Furthermore, this fluid does not carbonize ordecompose at high temperatures, does not evaporate and produce gasesunder the action of high temperatures or lowering of pressure. In otherwords, it is intended to use a high quality oil in the tappet, thatretains its good properties almost permanently.

An understanding of the invention may be Ihad from the followingdescription taken in connection with the accompanying drawing, in which,

Fig. l is a central vertical longitudinal section through a tappet madein accordance with my invention as it is assembled and beforeinstallation.

Fig. 2 is a similar section showing the tappet in operat ing position asinstalled in the engine and with its lower end bearing against anactuating cam.

Fig. 3 is a View like that shown in Fig. 2 showing the collapsedposition of the tappet which occurs when the engine is stopped with theactuating cam for the tappet at its extreme up position, and

Fig. 4 is a fragmentary transverse section substantially on the plane ofline lV-IV of Fig. 2 looking down- Wardly.

ite States Patent O Like reference characters refer to like parts in thedifferent ligures of the drawing.

In a preferred structural embodiment of my invention, a vtappet body lof cylindrical form is provided bored downwardly from its upper end butshort of the lower end thereof, the lower end of the body having aclosed end 2. Within the body and at the lower portion thereof is aspring actuated valve 3 of the form shown having a horizontal top and adepending cylindrical skirt 3a, the top at its edges extending outwardlybeyond the skirt 3a, providing a continuous annular flange 4 as shown. Acoiled compression spring 5 at its lower end seats against the bottom 2of the tappet and at its upper end is against the under side of theflange 4. The spring 5 is of a relatively light strength and mayapproximate four pounds. There is thus provided between the valve 3 andthe bottom of the tappet a chamber 6. Such chamber is not closed at itsupper portions, there being a narrow annular space 7 between theperipheral edges of the flanges 4 and the walls 1 of the tappet body.Also centrally of the top of the valve 3 a vertical opening 8 ofrestricted size is made. There is also a conducting passage 9` madethrough the depending skirt 3a of the valve 3 immediately below the topof the valve as shown in Figs. l to 3 inclusive, such passage connectingthe space surrounded by the depending wall or skirt 3a of the tappet 3with the upper portion of the chamber 6.

Within the upper portion of the tappet body 1 an outer piston is mountedfor up and down movements having a closed upper end or head and arelatively long cylindrical depending skirt as shown, the lower end otwhich serves as a valve seat for the upper side ofthe flange 4 of valve3. The lower end port-ion of the skirt is reduced exteriorly indiameter. providing an annular space at 11 around its lower portion.Adjacent the upper closed end of the outer piston 10 an annular grooveis made in which a sealing ring 12 of silicone rubber is located whichsnugly engages the bottom of the groove and the inner side of thevertical wall of the tappet body 1 to provide a secure seal againstupward passage of the oil which is used in the tappet. A silicone rubberseal is used because it is a material that is most resistant to theeffects of heat and oil, thus providing an effective seal for a longperiod of time.

The upper end of the piston 10 has a generally semispherical recess 13therein to receive the lower rounded end of a push rod 15, whichactuates the usual rocker arm, and in turn, the engine valve, of anoverhead valve engine. A retaining split ring of spring wire material,as at 14, seats in an interior horizontal groove of the wall of thetappet body 1 to limit the upward movement of the piston 10, and holdthe assembly together.

An inner piston 16 is within the outer piston 10, having reciprocatingmovements within the depending skirt thereof. It has a lower head and anupwardly extending cylindrical skirt. In the lower head an annulargroove is made and a second sealing ring 17 of silicone rubber istherein to make a seal between the chamber at 18 which is between thelower end of the head of the piston 16 and the upper side of the Valve3.

A heavy coiled compression spring 19 has its lower end portion receivedwithin the upwardly extending skirt of the piston 16, at its upper endbearing against the under side of the head of the piston 10. Such heavyspring, of approximately fteen pounds weight under compression, when thetappet is in operation, has a tendency to force the inner piston 16 in adownward direction. The cham ber Ztl Awithin which the spring 19 islocated has air therein."y

In assembling the tappet, the body 1 is partially lled with silicone oilsuicient that it will ll the chambers 6 and 18. The valve 3 with thespring 5 thereon is dropped into the body. The air trapped under thevalve 3 will escape upwardly through holes 8 and 9, after a short time.`The piston 16 is'assembled into piston-10 before the latter is put intothe tappet body, and they will be located with reference to each othersuch that the lower side of the head of the piston i6 will reach to andproject slightly beyond the lower open end of the skirt of piston l0.When this piston assembly is put into the body It, air is forced out ofthe body. When the lower face of inner piston i6 reaches the top surfaceof the oil, any air remaining'in the body is in the annular space ill,from where it can be forced out past thel piston 10. It is importantthat all of the air be removed from the oil chamber and if necessary,this can be done by creating a vacuum above the tappet to suck out thelast traces of air. After this is done, and with the lower face ofpiston 16 on the oil, any further downward movement of piston 10 causesa relative upward movement of piston 16, and compression of spring 19,to provide room for oil moving from chamber 6, Athrough hole 8, intochamber i3. The air in chamber 20 is also compressed slightly by theupward movement of piston 16.

When the outer piston i is forced downwardly a sufficient distance tobring its top surface below the groove that receives locking ring M, thering is put into position and the assembly is completed.

The assembled tapped, as shown in Fig. l, is installed in an engine, andarranged for reciprocation in a bored hole in the block, fragmentarilyindicated at 21 in Fig. 2. The lower end of the engine push rod 15 isseated in the seat 13, and the base 2 of the tappet body 1 rides againstthe engine cam 22 below it, which, upon rotation of the shaft raises andlowers the tappet, thereby opening and closing the engine valve, throughthe action of the push rod and rocker arm. In opening the valve, theengine valve spring associated with the valve exerts a pressure of 100pounds or more through the push rod 15 to the tappet. This force againstpiston l0 causes it to move downward, but -only a small amount becauseof the rapid rotation of the camshaft, which may vary from 200 R. P. M.at idle speed to 2000 R. P. M. at fast speed. Downward movement of thepiston 10 is controlled by the amount of oil that can pass through smallhole 8 during the short interval of time the cam is in the up position.

When the cam is lowered, permitting the engine valve to close, there isno longer any pressure downwardly against piston 10; in fact, due to thepassage `of oil through hole 8 while the cam was up, there is now aslight clearance between the socket 13 and push rod 16. Under thiscondition, spring i9 expands and takes up this clearance by pushingouter piston l0 upward and inner piston 16 downward. The downwardmovement of piston 16 causes valve 3 to separate from its seat, thuspermitting oil to flow quickly from chamber i8 back to chamber 6. Whenthe pressures are substantially equalized, spring forces valve 3 againstthe seat, and the tappet is again ready for the next lifting of the cam.The transfer of oil from chamber 6 to chamber 18 through small hole 8,during the lifting of the cams, is very small in amount; the downwardmovement of piston during this cycle might range from .001l to .008depending on the temperature of the engine and the speed at which theengine is running. This slight leakage of oil prevents the engine valvefrom being held open as the various parts of the engine increase intemperature and consequently in size, in running an engine from cold tomaximum operating temperature.

When an engine is stopped, certain cams on the carnshaft come to rest inthe up position, Or partially so. Such a condition is shown in Fig. 3.When this happens, the tappet on that cam stops with the engine valvespring pressure steadily forcing the piston 10 downward. As oil leaksthrough Ithe small opening 8 from chamber 6 to chamber 18, due to thesteady pressure of the valve spring, piston 10 and valve 3' are forcedto the bottom of the tappet body, to the position shown in Fig. 3. Toprovide room for the oil that was forced from chamber 6 to chamber 18,inner piston 16 is forced upward, further compressing spring 19, and theair between the two pistons. The silicone rings keep the oil fromleaking past the pistons.

When the engine is started and the cam 22 turns to the down position,spring 19 quickly expands, keeping piston 10 in contact with the pushrod, forcing the inner piston i6 downward, and causing the valve 3 toseparate from the valve seat at the bottom of piston itt). Thisseparation allows chamber 6 to be rapidly filled again, then spring 5closes valve 3 against its seat.

During operation of the engine, any llow of oil through the passage 8 ineither direction is minor and inconsequential in its effects, but at alltimes a balancing of pressures in the chambers 6 and 18 is substantiallymaintained.

The construction described is very practical and economical from bothutility and production standpoints. The sealing rings 7 and i2, ofsilicone rubber, are durable, and are not dissolved or otherwiseadversely affected by the heat of the engine, or by the silicone oilinside of the tappet, or the engine oil that might come in contact withit from the outside. By means of one piston sliding within the other, aconstant Volume of space is maintained for the fixed volume `of oilcontained in the tappet. The tappet is self-adjustable and eliminatestappet Vnoises during engine operation.

The invention is defined in the appended claims, and is to be consideredcomprehensive `of all forms of structure coming within their scope.

I claim:

l. A hollow cylindrical Itappet body open at its upper end and closed atits lower end, a valve within the lower portion of said body having ahorizontal closed upper end and a downwardly extending annular skirt,said closed upper end having a generally centrally disposed restrictedopening therethrough, a relatively light coiled compression springbetween said valve and the closed end of said body, an `outer pistonwithin the body having an upper closed head and a depending cylindricalskirt extending to said valve, said valve being normally lifted by saidspring to engage against the lower end of said skirt, an annular sealingring between said piston and the tappet body, an inner piston within theskirt of the rst piston having a lower closed head and an upwardlyextending skirt, an annular sealing ring between the inner piston andskirt of said outer piston, and a rela-tively heavy coiled compressionspring between the heads of said inner and outer pistons, said tappetbody, from its closed lower end to the lower side of the head of saidinner piston being lled with liquid, and the space between the heads ofsaid pistons with air.

2. A hollow cylindrical tappet body open at. its upper end and closed atits lower end, an outer piston within said body against the upper end ofwhich an engine valve stem is adapted to pressure engage, an innerpiston within and vertically movable with respect to the outer piston,spring means between said pistons tending to normally move the innerpiston toward the inner end of said outer piston, sealing means betweenthe outer piston and said tappet body, sealing means between thepistons, a horizontal valve within and across the tappet body at theinner end of the outer piston, said valve having a restricted passagetherethrough from lower to 'upper side below the inner piston, springmeans between the valve and closed end of said tappet body pressing saidvalve against the lower end of said outer piston, the lower portion ofsaid tappet body below the inner piston being lled with liquid, and saidvalve at its edges being spaced a short distance from the inner sides ofthe tappet body.

3. Structure having the elements in combination defined in claim 2, saidouter piston at its lower end portion having reduced thickness toprovide an annular space between the lower end of said piston and thetappet body, and said valve having downwardly extending support meansadapted, at the lowermost position of the valve to rest against theclosed end of said tappet body.

4. A hollow cylindrical tappet body open at its upper end and closed atits lower end, -a piston movable within said body against the upper endof which an engine valve stem is adapted to pressure engage, a secondpiston within the first piston, a relatively strong compression springbetween said pistons, said pistons being above the closed end of saidbody, the space between said pistons and closed end of the body beingfilled with liquid, and the space between the pistons with air, a springactuated valve pressing upwardly against the lower end of the firstpiston dividing the liquid filled space into two chambers, said valvehaving a restricted liquid vent passage therethrough connecting saidchambers, and sealing means operatively associated with each pistonpreventing passage of fiuid past said pistons.

5. In a hydraulic tappet, a hollow tappet body, a piston located in saidbody against the upper end of which the lower end of an engine valvestern is adapted to bear, movable means within said piston closing anexpansible and contractable air chamber therein in its upper portion,there being a liquid chamber between said means and the tappet bodybelow said air chamber, spring means tending to move said means toexpand the air chamber, a valve dividing the liquid chamber into twoparts, one in the piston below the air chamber and closed by said valveand the other between the valve and the lower end of said tappet, springin closed position normally holding the valve means against said piston,said valve having a restricted liquid control passage therethroughconnecting the two divided parts of said liquid chamber, and meanssealing against escape of liquid or air from said liquid and airchambers.

6. Structure as defined in claim 5, said liquid within the tappet bodybeing silicone oil having low viscosity change under temperaturechanges, and high stability under normal internal combustion engineconditions.

7. A valve tappet comprising, a hollow body closed at its lower end, apiston in said body against which an engine valve stem is adapted toengage at the upper end thereof, a second piston in the body betweenwhich and the first piston an air chamber is made and between the secondpiston and` the lower end of the tappet body a liquid chamber is made, acompression spring between the pistons, a valve dividing the liquidchamber into upper and lower parts, said valve having a liquid meteringpassage of restricted area connecting the two parts of the liquidchamber, a compression spring of less strength than the first springbetween said valve and the lower end of said body normally holding saidvalve against the lower end of said first piston, said first piston atits lower end reaching to and bearing against the upper side of thevalve, and sealing means for preventing escape of air or liquid fromsaid chambers.

References Cited in the file of this patent UNITED STATES PATENTS2,325,932 Banker Aug. 3, 1943 2,438,631 Bergmann Mar. 30, 1948 2,442,566Huferd June 1, 1948 2,442,575 Vandervoort lune 1, 1948 2,460,651 PaquinFeb. 1, 1949 2,570,854 Pierce Oct. 9, 1951 FOREIGN PATENTS 121,417Australia May 16, 1946

